496 BACTERIOLOGY. 



weak, and the testing for strength is still very crude, 

 full doses of serum should be given if the case is at all 

 serious, for the dose is limited only by the amount 

 of horse-serum which we feel it safe to give, not be- 

 cause we have sufficient protective substance. 



Bacteriological Diagnosis. Streptococci, using the 

 name in its broadest sense, can often be demonstrated 

 microscopically by simply making a smear preparation 

 of the suspected material and staining with methylene- 

 blue solution or diluted ZiehPs fluid. In order to 

 demonstrate them microscopically in the tissues, the 

 sections are best stained by Kuhne's methylene-blue 

 method. In all cases, even when the microscopical 

 examination fails, the cocci may be found by the culture 

 method on plate agar or slanted agar at 37 C. To 

 obtain them from a case of erysipelas it is best, accord- 

 ing to Fehleisen, to excise a small piece of skin from 

 the margin of the erysipelatous area in which the cocci 

 are most numerous; this is crushed up and part of it 

 transfered to a gelatin tube and to the melted agar in 

 another tube. After shaking thoroughly the contents 

 are poured out into Petri dishes. The gelatin is kept 

 at a temperature of 20 C. At the end of two or 

 three days numerous small colonies develop in the 

 vicinity of the particles of skin. The agar plate is 

 kept at 37 C. for twenty-four hours. It is usually 

 sufficient, however, to make a streak culture on agar in 

 a Petri dish with the crushed excised portion of skin 

 and place this in the incubator at 37 C. 



In septicaemia the culture method is always required 

 to demonstrate the presence of streptococci, as the micro- 

 scopical examination of specimens of blood is not suffi- 

 cient. For this purpose from 3 to 5 c.c. of the blood 

 should be drawn from the vein of the arm aseptically 



